U.S. Pat. No. 6,529,817 describes a device for detecting a knock in a combustion engine.
Conventionally, the amplifier used for amplifying the knock sensor signal has a fixed gain. As the knock sensor amplitude varies over a wide range, the amplification of the signal with a fixed gain will result in loss of resolution under some conditions.
German Patent Document No. 102 20 600 describes a device in which the gain of the amplifier is adapted after processing the knock signal for knock detection.
U.S. Pat. No. 5,040,510 describes a method in which the gain of the amplifier is stored as a function of engine RPM and adapted accordingly.